All web references are accessed on March 24, 2019
Municipal Fluoridation of Drinking Water
In Part 3, I showed how Durham Region in Ontario fluoridates much of its water supply with “hydrofluosilicic acid.”
According to https://en.wikipedia.org/wiki/Hexafluorosilicic_acid, the simplified formula for this chemical is Na(2)SiF(6), and its alternative names are:
- hexafluorosilicic acid (preferred IUPAC name)
- fluorosilicic acid
- fluosilic acid
- hydrofluorosilicic acid
- silicofluoric acid
- oxonium hexafluorosilanediuide
- oxonium hexafluoridosilicate(2−)
The list comes close but doesn’t include the exact variant of the name used in the municipal documents which I’m trying to stick with – hydrofluosilicic acid. In any case, Wikipedia does have a redirect page for this name: https://en.wikipedia.org/w/index.php?title=Hydrofluosilicic_acid&redirect=no.
The confusion involved in something like this is off-putting, and it reminds me of the way in which Canadians are immersed in two contradictory measurement systems in our daily lives–Metric and Imperial: pounds vs. kilograms, feet vs. meters, centimeters vs. inches. In another article, I wrote about Brave New World standardization, but I think part of what we live with is a Brave New World caste system, in which we are being hobbled to one degree or another by a lack of simple standards about important areas of knowledge. Ideally, most people should be able to gain an understanding of the world around them without being deterred by confusion in spelling and terminology, or other barriers. I believe also that the modern academic system has been set up to create a harmful specialization and lack of interaction between different areas of knowledge (further research).
According to the same article, hydrofluosilicic acid is
commonly used as a source of fluoride for water fluoridation
only available commercially as solution
By the way, if this chemical is combined with sodium hydroxide (NaOH), another product is produced, a fluorosilicate salt Na(2)SiF(6), which is also used for water fluoridation according to the article.
With hydrofluosilicic acid
. . . At the concentration usually used for water fluoridation, 99% hydrolysis occurs and the pH drops. The rate of hydrolysis increases with pH. At the pH of drinking water, the degree of hydrolysis is essentially 100%.
H2SiF6 + 2 H2O → 6 HF + “SiO2”
In this equation, HF refers to hydrofluoric acid, which is solution of hydrogen fluoride in water.
Quoting from Wikipedia:
Hydrofluoric acid is a solution of hydrogen fluoride (HF) in water. It is a precursor to almost all fluorine compounds, including pharmaceuticals such as fluoxetine (Prozac), diverse materials such as PTFE (Teflon), and elemental fluorine itself. It is a colourless solution that is highly corrosive, capable of dissolving many materials, especially oxides. Its ability to dissolve glass has been known since the seventeenth century . . . high reactivity toward glass and moderate reactivity toward many metals . . .
Hydrogen fluoride gas is an acute poison that may immediately and permanently damage lungs and the corneas of the eyes. Aqueous hydrofluoric acid is a contact-poison with the potential for deep, initially painless burns and ensuing tissue death. By interfering with body calcium metabolism, the concentrated acid may also cause systemic toxicity and eventual cardiac arrest and fatality.
Hydrogen fluoride is a highly dangerous gas, forming corrosive and penetrating hydrofluoric acid upon contact with moisture. The gas can also cause blindness by rapid destruction of the corneas.
. . .
Upon contact with moisture, including tissue, hydrogen fluoride immediately converts to hydrofluoric acid, which is highly corrosive and toxic, and requires immediate medical attention upon exposure. Breathing in hydrogen fluoride at high levels or in combination with skin contact can cause death from an irregular heartbeat or from fluid buildup in the lungs.
So, getting back to hydrofluosilicic acid, https://en.wikipedia.org/wiki/Hexafluorosilicic_acid contains the following health and safety information:
Hexafluorosilicic acid can release hydrogen fluoride when evaporated, so it has similar risks. Inhalation of the vapors may cause lung edema. Like hydrogen fluoride, it attacks glass and stoneware. The LD50 value of hexafluorosilicic acid is 430 mg/kg.
LD50 is explained here: https://en.wikipedia.org/wiki/Median_lethal_dose:
In toxicology, the median lethal dose, LD50 (abbreviation for “lethal dose, 50%”), LC50 (lethal concentration, 50%) or LCt50 is a measure of the lethal dose of a toxin, radiation, or pathogen. The value of LD50 for a substance is the dose required to kill half the members of a tested population after a specified test duration. LD50 figures are frequently used as a general indicator of a substance’s acute toxicity. A lower LD50 is indicative of increased toxicity.
. . .
The LD50 is usually expressed as the mass of substance administered per unit mass of test subject, typically as milligrams of substance per kilogram of body mass . .